FR2685447A1 - IMPROVED GRID BURNER AND HEATING INSTALLATION EQUIPPED WITH SUCH A BURNER. - Google Patents

Abstract

Gas burner comprising a gas distribution chamber (3) supplied with combustion air and fuel gas and communicating with a combustion chamber (15) through a main flame stabilization grid (11) having a lacunar structure, porous to the mixture air / gas. Preferably, the means (23) for igniting the burner will be placed outside the distribution chamber but will pass through the grid (11), the ignition being carried out either from one side of this grid, or from of its periphery. Such a burner can in particular be used with a compact submerged tube on an industrial bath heating installation.

Description

The invention relates to a mixing burner.

  I have az and grate (s) of combustion usable especially on submerged tube heating systems. More specifically, the invention relates firstly to a gas burner comprising: a distribution chamber for promoting the mixture of combustion air and fuel gas, a combustion chamber communicating with the distribution chamber, interposed between them a flame-stabilizing grate, a combustion air inlet for supplying air to the distribution chamber, and a fuel gas inlet for supplying the same distribution chamber with gas, said flame-stabilizing grating having first orifices for relatively wide cross section, for the passage of the mixture of air and

  of gas to the combustion chamber.

  Many heating equipment for industrial baths using the technique are known today.

compact submerged tubes.

  Often, these equipment use so-called "nose-mix" burners, that is to say without distribution, the combustion taking place directly in the zone where the air

and the gas meet.

  However, experience has shown that this type of burner is not completely satisfactory, especially on compact submerged tube installations and often leads to excessive production of carbon monoxide, as well as to noisy operation due in particular to

turbulence problems.

  The applicant has already proposed, particularly for this type of problem, some solutions, one of which is set forth in the French patent application FR-A-2 606 492 filed

November 7, 1986.

  With a permanent goal of improvement, the applicant is now proposing an improved combustion and heating installation, which is even more reliable and easier to maintain, given the increasing requirements in this area. This equipment also makes it possible to increase the overall efficiency of the installation by increasing the

  intrinsic performance of the burner.

  The solution proposed in the invention consists in particular that the grid of this burner is traversed not only by said first orifices, but also by second orifices of smaller section giving the grid a lacunar structure, porous to the air / mixture. gas that flows through these two series

orifices.

  Advantageously, these orifices will be distributed over substantially the entire surface of the gate, the number of second orifices being much greater than that of the first, so that, with the burner operating, the flames developed in the combustion chamber comprise relatively great length substantially in the extension of the first orifices and a zone of relatively short flames,

  distributed opposite said second orifices.

  In this way, the combustion efficiency should be optimum and the classical problems of

  flame stability much less important.

  A priori, the grid can be made from materials and structures belonging to the following list: sintered bronze or stack of metal sheets

  finely perforated, fibrous ceramic, metallic fabric.

  According to another characteristic of the invention, the burner will also comprise, advantageously, ignition and flame control means disposed adjacent to the distribution chamber and opening into the combustion chamber. Preferably these ignition and control means will receive the mixture flow necessary for ignition via an ignition chamber isolated or separate from the distribution chamber with independent or autonomous power supplies to allow dosages

  air / gas specific to each of these rooms.

  To ignite the burner, it will be possible to resort either to a "local" ignition offset towards the outside of the main gate, or to a peripheral ignition by a zone of flames then bordering the periphery of the chamber

of combustion.

  In order to promote the mechanical resistance over time in particular of the main gate, in particular with respect to thermal stresses, another characteristic of the invention provides for the provision of a brewing turbine for

  gas in the distribution chamber.

  In addition to the burner which has just been presented, the invention also relates to an installation for heating a bath of liquid heated by such a burner whose combustion chamber immersed in said bath is connected to at least one tube-exchanger also immersed in this bath and in which can circulate, before their evacuation, the combustion products generated by the burner. In what follows, an embodiment of the invention will now be described in greater detail, with reference to the accompanying drawings given solely by way of nonlimiting examples and in which: FIG. a schematic local view of the burner of the invention in a section along the line II of Figure 2, Figure 2 is a top view of the same burner in the direction of the arrow II of Figure 1, the figure 3 is an enlarged local plan view of a porous grid usable in the context of the invention; FIG. 4 is another local view of the burner of the invention along the section line IV-IV of FIG. Figure 5 is a schematic view of the burner of the invention used in a compact submerged tube installation, and Figure 6 illustrates an alternative embodiment. Referring firstly to FIGS. 1 and 2, the burner marked as a whole 1 comprises a distribution chamber (also called a "premix" chamber) into which, by a preferably radial opening, the combustion air and the combustible gases that start to

to mix.

  In 7, the arrival of combustible gas whose flow is directed, via at least one transverse opening front 7a or rear 7b (Figure 2), substantially parallel to the flow of air under pressure (blown air) which

arrives by the radial pipe 9.

  The distribution chamber 3, which has the general shape of a cylindrical well with a substantially circular cross-section, is limited transversely on its front face (AV) by a flame-stabilizing grid 11 through which the mixture of air and gas passes, after passage of the latter through a baffle or chute 12 of defined or limited distribution by a plate or any other transverse obstacle 13 favorable to the homogeneous mixture

gases.

  The grid has the function of ensuring a suitable distribution and good stabilization of the flames at the entrance of the combustion chamber 15 o go

to develop these flames.

  To favor this, and as can be seen more clearly in FIG. 3, this grid, which here has the general shape of a substantially flat plate, has been constructed to be traversed over its thickness e, preferably by two series of orifices comprising first orifices 19 a of relatively large section (a few m M 2), as well as second orifices 19 b of smaller section giving to the

  grid a lacunary structure, porous to the air / gas mixture.

  In practice, these two series of orifices will advantageously be distributed over substantially the entire active surface of the gate And the number of second diffusion orifices 19b will be much greater than that of the main orifices 19a, for example in a ratio substantially comprised between 15 to 1 and 30 to 1 As to the cross section of these second orifices 19 b, it will preferably be 2 to 4 times smaller than that of the first

orifices 19 a.

  In this way, the burner operating, the flames developed in the combustion chamber (the cross section of which will preferably be slightly smaller than that of the grid) will comprise relatively long darts 21a extending substantially in the extension of the first orifices 19a, while a general zone of relatively short flames 21b is

  divide opposite second orifices 19 b.

  In practice, the grid may in particular be made from materials and structures of the sintered bronze type or stack of finely perforated metal sheets or fibrous ceramics or fabric

metallic.

  For example, in the context of a sintered bronze grid, provision may be made to use a plate made of this material approximately 3 mm thick, pierced with holes of 2 mm in section with a square pitch of 8 mm, the degree of

  vacuum corresponding to these holes being about 3 to 8%.

  The tests have shown that a grid of this kind was very good, whose power represented by the small diffusion holes 19b represented approximately 30 to

% of the total power.

  It should be noted that a complementary advantage of such a structure is to ensure internal cooling

  by circulating through it the air / gas flow.

  One could even provide that the second orifices 19b, advantageously arranged substantially regularly through the surface of this grid, open for some of them randomly on this or that main orifice 19a, thus increasing the section thereof, as is illustrated for example at

  the location of the orifice 19 al of FIG.

  Returning to the structure of the burner of FIGS. 1, 2 or 4, it will also be noted that it comprises, in a conventional manner, ignition means 23 making it possible to start the combustion, as well as control means 25 of the

presence of flames.

  The ignition means may for example consist of a candle, the type of car candle,

  climb through the main gate 11.

  As the control means 25, these ignition means will preferably be arranged outside, next to

of the distribution chamber 3.

  More specifically, the igniter 23 may be disposed at the location of a passage 27 (see Figure 4) formed on the side, through the gate 11, this passage receiving a portion of the burner head forming an igniter holder 29 equipped with autonomous arrivals of fuel gas 31 and combustion air 33 (see FIGS. 1 and 2) for supplying an ignition mixing chamber 35 This chamber, preferably separated or isolated from the distribution chamber by a wall 36, may communicate with the combustion chamber 15 through a complementary gate 37 for stabilizing the ignition flame, this gate then extending substantially parallel to the plane of the main gate 11 and being traversed by the igniter 23, so that the electrodes 23a of the latter open into the combustion chamber 15 to ignite the mixture. Thus disposed, the igniter 23 will preferably extend substantially parallel to the general axis 39 of

  the chamber 15, rather towards the periphery of the grid 11.

  As for the ignition chamber 35, it may be in the upper part in the form of a vertical hollow column, annular, surrounding a central cavity open to the air of the igniter support, the head 23b of the igniter With its supply cable 41 extending into this central cavity. Furthermore, thanks to a tangential supply of air at its upper part, this same chamber will provide a mixture by rotating the gases until they meet, in lower part, the transverse grid 37 at the place where the ignition chamber

takes the form of a disc.

  In order to check the presence of the flames in the combustion chamber, the burner may therefore also be equipped with a control means 25 whose probe, consisting for example of an electrode 25 preferably of rectilinear shape, will extend into the zone of development of the flames respectively attached to the main gate 11 and the secondary ignition gate 37, as appears

clearly in Figure 4.

  Thus disposed, the control means 25 can pass through a well 43 passing through a second passage 45 formed through the main gate 11 so that the probe 25 can communicate with the combustion chamber, the head 25b of this means of control with its power supply cable 47 of course remaining away from the combustion zone to be cooled by the air

ambient.

  Comparing FIGS. 1 and 4, it will also be noted that the main grid will advantageously be kept at its periphery by an externally extending flange 49, substantially at the level of the connection being removable between the upper part of the burner comprising the combustion chamber. breakdown 3 and the part

  lower part comprising the combustion chamber 15.

  To do this, the flange 49 will define locally

  an annular cavity 51 external to the chambers 3 and 15.

  In this cavity, a retaining means 53, such as a circlip, can maintain with some possible play the

  peripheral edge of the grid 11.

  Thus, the holding zone of this grid will be relatively thermally insulated from the hot part of the burner and the grid will be able to absorb more

  easily thermal stresses.

  Let us now look at Figure 5, to briefly describe the preferred application of the burner 1 of the invention to the heating of an industrial bath of liquid 55 o are immersed at least the combustion chamber 15 of the burner and a tube heat exchanger 57 connected to the outlet 15a of the combustion chamber 15 and which winds in the bath 55, which is heated by heat exchange with the combustion products generated by the burner and circulating in the tube before being discharged to

the outlet 57a of this same tube.

  FIG. 6 shows a variant embodiment of the burner of the invention which is characterized

  by a mixing turbine and a peripheral ignition.

  This burner, marked 10 comprises, as before, a distribution chamber 30 communicating with a combustion chamber 32 through a main combustion grate 34 of the same type as the previous one

(11).

  The distribution chamber 30 is here fed tangentially with air and fuel gas (already at least partially preferably mixed) via an intake manifold 38 that can be output upstream of the inlet

  38 a air on which is connected the gas inlet 38 b.

  To improve the quality of the combustion and to promote a good resistance to the thermal stresses of the gate 32, it has been placed opposite it, in the chamber 30, a stirring turbine 40 It has appeared preferable to place this turbine substantially at the level of the zone, opposite to the grid, where the lateral pipe 38 connects

tangentially to the chamber 30.

  In this way, the blades of the turbine will be able to receive the gas mixture transversely and thus be naturally driven in rotation by creating recirculation currents favorable to homogenization

  gases and the limitation of thermal stresses.

  A boss 42 located in FIG. 1 towards the top of the chamber 30 supports the rotation shaft 44 of the turbine, which can rotate therein conventionally, via

  ball bearings (not shown).

  For ignition of the burner, the solution adopted here consists of a "peripheral" ignition, via an ignition chamber 46 extending around the distribution chamber 30, a priori essentially in its part

before (AV).

  In particular in order to be able to regulate at will and autonomously the air and the gas respectively supplying the distribution and ignition chambers, it appeared again preferable to "isolate" them from one another by a partition wall 48 and to ensure the ignition chamber 46 its own arrival mixture, via a

  tangential feed pipe 50.

  And, for the attachment of the ignition flame, a secondary combustion grid 52 has also been interposed between the ignition chamber and the combustion chamber.

combustion.

  Since the distribution and ignition chambers are preferably arranged concentrically, this secondary grid may in particular be in the shape of a

  frame or crown surrounding the main gate.

  Such an arrangement is advantageous. Indeed, if we mount the aforementioned means 23, 25 ignition and flame control in the chamber 46, so that they pass through the gate 52 to open into the chamber 32, it will be possible no only to ensure an effective peripheral ignition, but also to improve the control conditions by limiting the thermal stresses supported by these accessories For this it will suffice, when the ignition sequence of the burner start cycle will be completed and that this the last will be kept lit thanks to the detection of the flames, to cut the gas supply of

  room 46 maintaining its air supply.

  The flames hung up to the secondary grid 52 will then go out But the air will continue to escape through this gate to the combustion chamber, this air flow then constituting an excellent means of continuous cooling at least the candle 23 and

the control electrode 25.

  Note that this principle of air blowing after ignition is quite adaptable to the case of the burner of Figures 1 to 5 Similarly, the principle of the peripheral ignition could be retained on this burner, the ignition chamber 46 with its accessories can thus come around the base (marked 3 'in Figure 1) of the

dispatch chamber 3.

1 i

Claims (16)

  1 Gas burner comprising a distribution chamber (3, 30) for mixing combustion air and fuel gas, a combustion chamber (15, 32) communicating with the distribution chamber (3, 30), with interposition between they have a main flame-stabilizing grid (11, 34), a combustion air inlet (9, 38 a) for supplying the distribution chamber with air, and a fuel gas inlet (7, 38 b) for supplying gas to the same distribution chamber, said main grid (11, 34) having first orifices (19 a) of relatively large cross-section therethrough, for the passage of the mixture of air and gas towards the combustion chamber, characterized in that the grid (11, 34) further comprises second orifices (19b) of smaller cross section, giving the grid a porous, porous structure to said mixture, which thus circulates through both the first and the second second ports (19a, 19b).   2 burner according to claim 1 characterized in that the first and second orifices (19 a, 19 b) of the main gate are distributed over substantially the entire surface thereof, the number of said second orifices (19 b) being much larger that of the first, so that the burner operating, the flames developed in the combustion chamber comprise darts of relatively large length (21 a) substantially in the extension of the first orifices and a zone (21 b) of relatively   short distributed opposite said second orifices (19 b).   3 burner according to claim 1 or claim 2 characterized in that the main gate (11, 34) is made from the materials and structures belonging to the following list: sintered bronze or stack of perforated metal sheets, ceramic fibrous, metallic fabric.   4 burner according to any one of   Claims 1 to 3 characterized in that the second   holes (19b) of the main grid have a section approximately 2 to 4 times smaller than that of first orifices. Burner according to any one of   preceding claims characterized in that the   second orifices (19b) of the main grid are formed regularly across the surface thereof, some of them opening onto at least some of said first orifices (19a), thereby increasing the section of these.   6 Burner according to any of the   preceding claims characterized in that in the   distribution chamber (3) an obstacle (13) is interposed on the path of the gases going towards the chamber of   combustion, to promote their mixture.   Burner according to any one of   preceding claims further comprising means   (23), characterized in that these ignition means are arranged next to the distribution chamber (3) and pass through the main gate (11)   to open into the combustion chamber (15).   Burner according to Claim 7, characterized in that the ignition means (23) are mounted on an igniter support (29) enclosing an ignition mixing chamber (35) separated from the distribution chamber by a wall ( 36), said chamber which is autonomously supplied with air and combustible gas, communicate with the combustion chamber (15) of the burner through a passage (27) formed in the main grid (11) and across which is disposed a secondary grid (37) for stabilizing the ignition flame, itself traversed by said means ignition (23).   9 burner according to claim 8 characterized in that the ignition mixing chamber (35) has an annular portion surrounding a hollow central portion of the igniter holder (29) open to the air and receiving said ignition means (23), said annular portion of the ignition chamber which is fed tangentially with combustion air ensuring mixing, with rotation, air and fuel gas that it receives. Burner according to any one of   Claims 7 to 9 comprising control means (25)   of presence of flames equipped with a control probe (25 a), characterized in that they are arranged next to the distribution chamber (3), their probe passing through the main gate (11) to open into the chamber of combustion (15).   it Burner according to any of the   preceding claims characterized in that the grid   main (11) is held at its periphery by a flange (49) which extends at the level of the connection between the distribution (3) and combustion (15) chambers, which flange locally defines a substantially annular cavity (51) outside said chambers and o means (53) retaining, so relatively thermally insulated, maintains with some possible play the border device of said grid.   12 Burner according to any one of   preceding claims characterized in that the section   right of the combustion chamber (15) is slightly   less than that of the main gate (11).   13 Burner according to any one of   preceding claims characterized in that the air and   the combustible gas begin to mix upstream of the   distribution chamber (3, 34) where mixing continues.   14 Burner according to any one of   Claims 1 to 5 characterized in that said chamber   of distribution (30) is fed tangentially with air and gas and comprises a turbine (40) which promotes mixing and is conducive to mechanical strength in the   time of the main gate (34).   Burner according to Claim 14, characterized in that the turbine (40) is arranged facing the main gate (34), substantially at the level of the zone where the distribution chamber (30) is fed with air. via a lateral pipe (38).   Burner according to one of Claims 1 to   6 or 14, characterized in that the distribution chamber (3, 30) is surrounded by a peripheral ignition chamber (46) fed with air and with combustible gas and communicating with said combustion chamber (15, 32) for an ignition of the burner by the periphery of this combustion chamber.   Burner according to Claim 16, characterized in that the peripheral ignition chamber (46) communicates with the combustion chamber (32) with the interposition between them of a secondary combustion grid (52) through which means (23) are mounted. , 25) for igniting and / or controlling flames, and thus deported away from the main combustion grate (34).   18 Burner according to any one of   preceding claims characterized in that the   ignition (35, 46) and distribution chambers (3, 30) are isolated from one another by a wall (36, 48) with each of the ducts (5, 31, 33, 38, 50) d supply of air and fuel gas connected thereto, so that their air and gas proportions are independent one from the other.   19 Installation for heating a liquid bath comprising the burner according to any one of   preceding claims including the combustion chamber   (15, 32) immersed in said bath (55) is connected to at least one heat exchanger tube (57) also immersed in the bath and wherein circulate, before their evacuation, the combustion products generated by the burner.